Serv-U LDAP authentication

Dear Everyone,

Could anyone explain me about Serv-U MFT user's account?

Currently I have  serv-U and enable LDAP authentication.

And I can used LDAP user to login and I am strange why I can login using my ladp account without put password? and also can login with any password too?

why user can login with any password or blank?

Thanks everyone for help.